The overall aim is to study the differentiation of properties among different excitable tissues in different animals and in different stages of the development within the same animal. Actual proposed research is: (1) Analysis of Ca dependent action potentials. By using improved voltage clamp technique the selectivity of the Ca channel and the kinetics of the membrane current through the Ca channel will be examined in giant muscle fibers of a barnacle in order to elucidate the molecular mechanism of the Ca channel. Pharmacological differences between Ca and Na dependent action potentials will be examined in various tissues. The development of the Ca dependent action will be examined in the flight muscle of the flesh fly during its development. (2) Ion permeation mechanism of excitable membrane. The anion permeation mechanism will be studied in skeletal muscle fibers of stingrays. The differences of current-voltage relations at different loci of the nerve cell membrane will be analyzed in Aplysia ganglion. The possible alteration of the electric charge at the inner surface of the photoreceptor cell of a barnacle will be examined by using charged artificial ion carriers. The properties of tetrodotoxin insensitive Na chanels will be studied in puffer fish, California newts and leech. (3) Mechanism of transmission in the absence of spike. The transmission mechanism between the photoreceptor and the second cell will be studied in the lateral eye of a barnacle and also in the retina of a turtle. This is to analyze the case in which the presynaptic potential change is hyperpolarization and also to examine the hypothesis of continuous background release of the transmitter.